In response to NIDA PA-01-097, this application details an R03 project that focuses on the service utilization of formal healthcare, mental health, and social services for men on methadone who perpetrate intimate partner violence (IPV). The proposed study will examine barriers and enhancers of service utilization among male methadone maintenance treatment program (MMTP) clients who perpetrate IPV. Drug-involved men who perpetrate IPV lie at the heart of two critical public health issues, drug abuse and IPV, that exact enormous financial and societal costs. Perpetrators of IPV represent a significant proportion of drug-involved men that may have a greater number and/or unique spectrum of service needs that differ from non-violent, drug-involved men and that remain unmet due to lack of service utilization. These needs extend beyond drug abuse and IPV to include mental and physical health and other social service needs. Most of the prior studies with perpetrators of IPV have been carried out with samples obtained from batterers intervention programs. Thus, service utilization among a more general population of men who perpetrate IPV remains unexplored. The proposed research will build upon findings from the Men's Health Project (MHP), an ongoing NIDA-funded study (PI: El-Bassel) to examine over time the relationships among drug abuse, IPV, and HIV-related risks among a random sample of 355 men attending MMTPs in New York City (NYC). We propose to extend the MHP by reinterviewing MHP participants who perpetrated IPV to study factors that impact their service utilization, an area not addressed in the parent study. The proposed study also includes a qualitative inquiry with MMTP service providers to understand MMTP service providers' perspectives on factors that impede or promote service utilization among their male clients who perpetrate IPV, as well as identify potential targets of change in the MMTP service delivery system. Aims, hypotheses, and measurements in the proposed study are guided by the Network Episode Model, which conceptualizes utilization of formal services as a series of behaviors influenced by individual/social context, social network, and service system factors. This study will provide pilot findings for the development of an R01 study testing the efficacy of an intervention designed to increase service utilization among men attending MMTPs who perpetrate IPV.